13. Spion Kop Lookout

13. Spion Kop Lookout
Key facts about this geosite:



Spectacular vista of surrounding mountains and the township of
Queenstown
The geology of the area is composed of submarine lavas, volcanic ash and
sediments which formed on the floor of a shallow sea
Extensive faults can be observed along the flank of the ranges in the
distance
How to get there: The Spion Kop lookout is near the centre of Queenstown (Figure 1).
From Miners Siding, follow Hunter St uphill and turn left onto Bowes St, then do a sharp left
onto Latrobe St to a small car park, from where a short, steep track leads to the summit of
Spion Kop (named by soldiers after a battle in the Boer War). The rhododendron-lined
track features a rail adit near the car park, and the top of the hill has a pithead on it (Figure
2). From the summit there are extensive views of Queenstown, the Mt Lyell Mine and the
West Coast Range.
Figure 1. Location of the Spion Kop Geosite.
Figure 2. Recommended walking route to the Spion Kop Geosite in Queenstown.
Geosite Description:
Volcanoes: Yellowish rocks exposed on the lower slopes in front of you are the Lyell
Schists (Figure 3). They are part of the Mount Read Volcanics, a 200 km long belt of rocks
that hosts many of western Tasmania's ore deposits. They were erupted in the Middle
Cambrian period, about 500 million years ago, mostly as a thick pile of submarine lavas and
volcanic ash and sediments on the floor of a shallow sea.
Ore Deposits: During the volcanism, hot fluids, partly derived from seawater, were drawn
through the volcanic pile in a convection system probably driven by a deep body of molten
magma. The fluids formed the Lyell Schists by altering the original minerals in the volcanics
and depositing pyrite (iron sulphide), more valuable copper and silver sulphides, and gold. In
a 5 by 2 km area near Queenstown, the Lyell Schists host about twenty ore deposits, by far
the largest of which is Prince Lyell orebody located under the West Lyell Open Cut about 3
km northeast of here. The orebody contains about 300 million tonnes grading 1% copper,
0.3 g/t gold and minor silver and has been mined for over 100 years.
Figure 3. Old Mt Lyell smelter site from Spion Kop.
Rift Valley: Not long afterward, in the Late Cambrian to Early Ordovician periods, a rift
valley developed east of here. Today the original fault scarp forms the Great Lyell Fault,
which can be seen in front of you. Material derived largely from the erosion of mountains
comprising Precambrian quartzites and schists located to the east, filled the valley with
boulders and then sand, which today form the Owen Conglomerate, visible as the high
mountain peaks on the far side of the Great Lyell Fault. The Owen Conglomerate has a
characteristic pink to purple colour due to an abundance of hematite (iron oxide). A major
episode of deformation occurred in the Devonian period (about 390 million years ago) and
caused extensive faulting and folding of both the Mount Read Volcanics and Owen
Conglomerate. The North Lyell Fault formed during this event and is visible on the
southeast slopes of Cape Horn Spur (see Figure 4).
Great Lyell Fault
Cape Horn Mine
North Lyell Mine West Lyell Open Cut
North Lyell Fault
Mt Lyell
Sedgwick Bluff
Figure 4. Photograph of the West Coast Range showing the major fault structures.
Glaciers: The ragged skyline in front of you (Figure 5), developed in the Pleistocene epoch,
during several episodes of glaciation. In general the resistant pinkish Owen Conglomerate
forms the high peaks of Mt Lyell, Mt Owen and Sedgwick Bluff while the less resistant
Mount Read Volcanics are clearly evident by their characteristic yellow to brown
weathering colours on the lower slopes (Figure 6). The pebble and cobble deposits that
cover the summit of Spion Kop are also of glacial origin.
Sedgwick Bluff
Cape Horn
Spur
Mt Lyell
Philosophers
Ridge
Mt Owen
Figure 5. View of the skyline from Spion Kop with the key mountains and ridges indicated.
Figure 6. Mt Lyell and West Lyell Open Cut from Spion Kop highlighting the contrasting
appearance of the pinkish Owen Conglomerate on Mt Lyell and the yellow to brown
weathering Mount Read Volcanics in the foreground.